古脊椎动物学报2011，Vol.49Issue(2)：229-240,12.
甘肃董湾晚新近纪地层及中新统/上新统界线
LATE MIOCENE-EARLY PLIOCENE BIOSTRATIGRAPHY AND MIOCENE/PLIOCENE BOUNDARY IN THE DONGWAN SECTION,GANSU
摘要
Abstract
The Dongwan section is located near Dongwan Village, Qin' an County, Gansu Province (34°58′N, 105°47′E). The section is a continuous eolian red clay sequence and is dated from 7.3 to 3.5 Ma by paleomagnetic study. The 74.8 m long section is divided into 21 layers (0 to 20 ) and 39 species of small mammals are found from 40 fossil levels. Based on faunal composition of small mammals, especially the myospalacines, four biozones are recognized.Biozone I covers layers 0 ～ 7, ranges magnetic polarities from upper part of C3 Br. 1 n to the lower part of C3An. 2n, and spans from 7.3 to 6.5 Ma. The mammals found in this biozone include Quyania chowi, Ochotonoma n. sp. 1, O. primitiva, Ochotona minor, O. lagreli, Sicista sp., Prospermophilus orientalis, Sinocricetus zdanskyi, ? Kowalskia sp., Prosiphneus licenti, P.tianzuensis, Lophocricetus grabaui, Pseudomeriones abbreviatus, and Hansdebruijnia pusillus.Biozone 11 covers layers 8 ～ 14. It ranges from the lower part of polarity zone C3An. 2n to the base of C3n. 4n, and has a time span from 6.5 to 5.24 Ma. The fossils found in this bio zone include Sulimskia sp., Parasoriculus sp., Paenepetenyia cf. P. zhudingi, Ochotonoma n.sp. 2, O. primitiva , Ochotona minor, O. gracilis , O. plicodenta , Prospermophilus orientalis ,Sinocricetus zdanskyi, Prosiphneus eriksoni, Pliosiphneus lyratus, Chardina n. sp., C. sinensis,Pseudomeriones abbreviatus, Sicista sp., Apodemus sp., Hansdebruijnia pusillus, Chardinomys sp., and Allorattus sp. The beginning of biozone II is marked by the first appearance of Prosiphneus eriksoni in the depth of 59 m.Biozone Ⅲ covers layers 15 ～ 17, ranges from the base of C3n. 4n to the upper part of C3n.2n ( Nunivak), and spans the time from 5.24 to 4.55 Ma. Fossils found in this biozone include Erinaceus sp., Parasoriculus sp., Ochotonoma n. sp. 2, Ochotona minor, O. lingtaica, Trischizolagus mirificus, Sinotamias n. sp., Sinocricetus zdanskyi, Cricetinus mesolophidus, Mimomys tedhardi, Pliosiphneus lyratus, Chardina sinensis, C. truncatus, Mesosiphneus sp., Pseudomeriones abbreviatus, P. complicidens, Chardinomys sp., C. yusheensis, and Apodemus sp. The beginning of biozone Ⅲ is marked by the first appearance of Mesosiphneus sp. at 35.5 m.Biozone Ⅳ covers layers 18 ～20, ranges from the upper part of C3n. 2n to the top of the section, and has a time span from 4.55 to 3.5 Ma. The small mammals found in this biozone include Ochotonoma n. sp. 2, Pliosiphneus lyratus, Mesosiphaeus praetingi, Chardina truncatus, and Chardinomys nihowanicus. The first appearance of Mesosiphneus praetingi at the depth of 20.4 m marks the beginning of this biozone.Biozone Ⅰ and Ⅱ are correlated to the late Late Miocene, equivalent to Baodean, while biozone Ⅲ and IV are correlated to the early Pliocene, equivalent to early Yushean. According to the paleomagnetic study, the boundary of Miocene/Pliocene (5.33 Ma) is located at the depth of 35.5 m of the section, and coincides with the last appearances of Prosiphneus eriksoni and Ochotonoma primitiva. The Miocene/Pliocene boundary is 2 meters lower than the boundary between biozone Ⅱ and Ⅲ, which is marked by the earliest appearance of Mesosiphneus sp. Except Mesosiphaeus sp., the earliest records of Paenepetenyia cf. P. zhudingi, Apodemus sp. and Ochotona lingtaica are also found closely above the boundary ( 1 ～2.5 meters). About 3 meters below the boundary, Parasoriculus sp., Sulimskia sp., Pliosiphneus lyratus, Chardina sinensis and Chardinomys sp. appear, and O. plicodenta and Sicista sp. disappear. The continuous sequence and high density of fossil levels qualify the section as a candidate stratotype section of Yushean Stage.关键词
甘肃董湾/晚中新世-早上新世/生物地层/榆社阶/界线层型Key words
Dongwan/ Gansu/ Late Miocene-Early Pliocene/ biostratigraphy/ stratotype of Yushean Stage分类
天文与地球科学引用本文复制引用
刘丽萍,郑绍华,张兆群,王李花..甘肃董湾晚新近纪地层及中新统/上新统界线[J].古脊椎动物学报,2011,49(2):229-240,12.基金项目
国家自然科学基金项目(编号:40872018)、国家重点基础研究发展规划项目(编号:2006CB806400)和中国科学院化石发掘与修理专项资助. （编号:40872018）
